(1) Field of the Invention
This invention relates to a linear compressor, and more particularly, to a stator of a linear compressor in which upper-lower splited type cores are regurally arranged in a bobbin in such a manner that their inner surfaces form a real circle.
(2) Description of the Prior Art
In general, a linear compressor is used in a refrigeration system that provides refrigeration energy by undergoing a refrigerant the successive process of compressing, condensing, expanding and evaporating. The linear compressor has a linear motor, which is driven by electromagnetic force created by the alternate direction change of magnetic flux, to compress the refrigerant at high temperature and pressure.
FIG. 1 shows a cross-sectional view of a conventional linear compressor. As shown in the figure, the conventional linear compressor consists of a housing 10, a driving part generating a driving force in the housing 10, and a compressing part inhaling, compressing and discharging a refrigerant by using the driving force of the driving part.
The compressing part includes a piston 11 and a cylinder block 13 which has a compressing chamber 12 for accommodating the piston 11 that moves rectilinearly and reciprocally therein. On one end of the cylinder block 13 is mounted a cylinder head 16 in which an inhaling chamber 14 and a discharging chamber 15 are provided for guiding the refrigerant to the inside and outside of the compressing chamber 12, respectively.
The driving part includes a back iron 20 attached to the outer circumference of the cylinder block 13, a stator 30 disposed apart from the back iron 20 at a given interval, and a permanent magnet 21 disposed between the back iron 20 and the stator 30 to interact with the electric field created by the stator 30. The stator 30 includes a bobbin 31 of a cylindrical shape having grooves for winding coils at the outer circumference thereof, coils 32 wound in the coil winding grooves of the bobbin 31, a plurality of cores 33 inserted into the bobbin 31 on which the coils 32 are wound.
On one end of the piston 11 is provided a fixing shaft 11a with a frame 40 for fixing the permanent magnet 21. A resonant spring 41 for elastically supporting the piston 11 is connected to one end of the fixing shaft 11a to raise the compressing force of the piston 11.
In such a conventional linear compressor, the cores 33 are arranged radially along the outer circumference of the cylindrical bobbin 31. However, it is very difficult to arrange the cores 33, which are made by piling up electric steel plates, at the bobbin 31 regularly in such a manner that the inner surfaces of the cores 33 form a real circle. The cores 33 and a permanent magnet 21 are spaced out at a fine interval from each other. Accordingly, If the cores 33 are arranged irregularly so that their inner surfaces do not form a real circle, the interval between the cores 33 and the permanent magnet 21 can not be kept constant so that the performance of the compressor is lowered, and the damage of the parts may be caused by the friction between the cores 33 and the permanent magnet 21.
On the other hand, in order to solve the above problems, there is disclosed a stator of a linear compressor in the Korean Patent Laid Open No. 97-55136 as shown in FIGS. 2a and 2b. As shown in the figures, the bobbin 31 of a cylindrical shape has grooves for winding the coils at its outer circumference. On the upper and lower ends of the bobbin 31 are radially arranged a plurality of guide projections 34 at regular intervals, between which the cores 34 are mounted. The cores 33 are made by piling up electric steel plates of a .OMEGA.-shape.
Therefore, the cores 33 are guided by the guide projections 34 and arranged regularly at the bobbin 31 in the state that their inner surfaces form a real circle, so that the interval between the cores 33 and the permanent magnet 21 can be kept constant.
However, in such a conventional art, to mount the cores of the .OMEGA.-shape on the bobbin having the aforementioned shape is carried out satisfactorily, but it is not in the cores of a C-shape. That is, the size of the permanent magnet is decided in proportion to the longitudinal length of the cores, and the core of the .OMEGA.-shape has a larger longitudinal length than the core of the C-shape when the same size of the bobbin is used. As a result, a larger-sized permanent magnet is also used, so that the entire weight of the compressor and its manufacturing cost are relatively increased.
Because of this reason, it is advantageous that the C-shaped core which is able to be split into the upper and lower parts is adopted, compared with the .OMEGA.-shaped core. But, it is difficult to support the upper core and the lower core in such a manner that the cores' inner surfaces form a real circle by means of the shape of the bobbin that has the guide projections only at the upper and lower plates. In addition, it may be caused that the contact portions between the upper core and the lower core are not fitted exactly to each other, so that the interval between the cores and the permanent magnet is not kept constant.